This application relates generally to couplings and, more particularly, to a couplings used to transfer fluids between two conduits within gas turbine engines.
Because of heat generated during operation, gas turbine engines often include flexible couplings for transferring fluids, especially cooling air, between conduits. Such couplings permit misalignment of mating hardware during installation, and permit the conduits to thermally expand during engine operation. One type of known coupling includes a metallic inner cylindrical sleeve including spherically formed ends. The sleeve is supported for axial and angular movement within the coupling with a pair of coupling members. The coupling members attach to the sleeve and each member includes an end containing carbon sleeves.
The carbon sleeves include inner bores that permit the carbon sleeves to contact the spherical ends of the sleeve to prevent fluid from leaking from the coupling between the inner sleeve and the coupling members. Because the carbon sleeves have a lower coefficient of thermal expansion in comparison to the metallic inner sleeve, the inner sleeve may expand to a greater degree than the carbon sleeve. Over time, such continued thermal expansion may lead to excessive wear of the carbon sleeves and leakage of the coupling. Over time, eventually the seals may erode completely and metal to metal contact between the sleeves may occur. Such contact potentially increases vibrations within the coupling which may in-turn lead to a failure of the coupling. Because the carbon sleeves are not serviceable, the couplings must then be replaced to prevent the coupling from leaking.
To minimize replacement of the entire coupling, other known types of couplings include replaceable seals. These couplings include a combination of a split seal and a continuous seal for sealing around each end of the inner sleeve. See for example U.S. Pat. No. 5,106,129. The assembly of such seals is complex because the continuous seal is mounted on a silicone based o-ring to provide radial pressure to the inner bore and the split seal is mounted on a split metallic ring which is further mounted on a metallic wave spring. Each end of the inner spring is retained in a joint end with a retaining ring inserted within a groove extending into the joint end. To insert the seals into the grooves, unique tools are used to radially compress the seals. During each engine cycle, temperature differences existing between an engine""s casing and the conduits may cause the casing to thermally expand a greater amount than the conduit. This in turn may cause the coupling ends to move relative to the inner sleeve. Additionally, angular movement of the joint may occur because of the temperature differences between the casing and the conduits. Because the o-rings provide only a small amount of radial restitution, as the continuous seals wear, their effectiveness is reduced. As the split seals wear, leakage may occur, and the split seals are forced radially outward to compensate for the wear and reduce the leakage. However, these seals typically have a nominal flow leakage through the split seal.
In an exemplary embodiment, a coupling used to transfer fluid from one conduit to another conduit includes a seal arrangement that permits an inner sleeve to move axially and angularly, relative to the conduits, without fluid leaking from the coupling. The coupling also includes a pair of coupling members coupled to the inner sleeve to support the inner sleeve. The inner sleeve includes tapered ends including retaining grooves sized to receive a seal. Each coupling member includes a tapered end sized to compress each inner sleeve seal during assembly of the coupling. The seals each include a spherical lip that is outwardly biased to provide sealable contact between the inner sleeve and the coupling first and second members.
During operation, as the inner sleeve moves axially or angularly, the seal lips ensure that sealable contact is maintained between the inner sleeve and the coupling first and second members. Such an assembly facilitates eliminating fluid leakage from the coupling, and because the coupling members include tapered ends, assembly of the coupling is simple.